Maria Sharapova is hitting the sweet spot. The Williams sisters are seeing the ball well, while Novak Djokovic has had his first win. It's been Lleyton Hewitt and ''C'mon!'' And all this before a single ball has been hit in anger at the 2013 Australian Open.

In the days leading up the tournament, Melbourne has been buzzing with off-court appearances by the biggest names in the game in pursuit of the dollars that come with their endorsements. Each day brings a new event, and a new product to sell.

In Sharapova's case, it was the Australian launch of her own brand of lollies, Sugapova. Venus and Serena Williams were playing table tennis at the Olsen, the South Yarra hotel where they stay.

Djokovic's first ''win'' came when he hit a tennis ball faster than an Audi R8 LMS GT3 race car. Hewitt was spruiking his ''C'Mon'' range of apparel.

These may all seem sideshows to the main event. The tennis is the thing, right? Well, wrong, actually. In many cases, the world's leading tennis players earn more off the court than on.

In September, Forbes magazine published a list of the highest-paid tennis players, looking at their on and off court earnings. Out of the top 10, eight were making more money off the court - 75 per cent of earnings came from endorsements and appearance money. As Forbes noted, it is the global nature of a sport that is played all year combined with cashed-up fans that makes sponsorship so attractive.

But there is also the undisputed x-factor common to many of the great players, graceful and sometimes glamorous exponents of the game. The undisputed champion is Roger Federer, who, according to the list, made $US9.3 million on court, and $US45 million off court in the year to last July.

Of the women, Sharapova is the highest-paid, according to Forbes, winning $US5.1 million on the court, but earning $US27.1 million off it. Forbes reported her eight-year $70 million deal with Nike is the most lucrative in women's sport.

Her new line of lollies, Sugapova, takes her in a new direction. Launched at Crown last week, the gummy sweets were created by the player, who ''wanted to start something on my own; something that could bring the fun and passion of gummy candies to life and can be my own little project from start to finish''.

With only hours before the first ball of the first round, the off-court activity showed no sign of abating.

Late on Sunday, Caroline Wozniacki was helping launch the adidas by Stella McCartney range on a court made of mirrors. Across town, Sharapova and Li Na were on the red carpet for Crown's IMG players' party.

- Sydney Morning Herald